Stabilized polyalkylene oxide sensitized emulsions



United States Patent 7 Claims. (61. 9s 109 The invention relates to the stabilization of photographic materials which contain at least one silver halide emulsion layer sensitized with an alkylene oxide polymerization product, using a stabilizer combination of a known stabilizer and ortho-hydroxybenzylidene or orthohydroxy benzylamine derivatives.

It is known that the general sensitivityor" photographic silver halide emulsions may be increased by alkylene oxide derivatives, for example, ethylene oxide polymerisation products. The alkylene oxide derivatives are, however, of limited utility since they produce a considerable fogging and since they impair the keeping properties of the emulsion. Such emulsions chemically sensitized with polyalkylene oxide derivatives, in particular highly sensitive silver halide emulsions, show a considerable loss of sensitivity upon storage.

To overcome these defects, it has already been proposed to use these polyalkylene oxide derivatives together with certain stabilizers, such as organic mercury compounds, tetrazaindenes, tetrazaindoles, pentaazaindenes and urazole's as Well as par-abanic acid and phenols and diphenols.

These stbilizer additives have the disadvantage that although they partly reduce the fogging and partly reduce the loss in sensitivity of the photographic materials sensitized wit-h polyalkylene oxide derivatives during storage, they never quite eliminate both these defects, even if they are applied in combination with each other.

It is an object of the invention to provide stabilized photographic silver halide emulsions which have increased sensitivity of the type commonly attributed to chemical sensitization, without such concomitant increases in fog or poor keeping quality as might seriously affect the usefulness of the emulsions. Other objects of the invention will become apparent from a consideration of the following description and examples.

This object has been achieved by employing lightsensitive materials which are chemically sensitized by the addition of polyalkylene oxide sensitizers and which are stabilized by the addition of a basic stabilizer known per se and which further contain an ortho-hydroxy benzylidene or ortho-hydroxy benzylamine derivative of the general formulae:

and

wherein X represents an alkylene group with preferably up to carbon atoms or an arylene group preferably phenylene; R stands for a sulfo group, carboxylic group an OSO H group or salts thereof. The benzene ring 3,321,312 Patented May 23, 1967 of the general formulae as well as the substituent X may in turn be substituted. The following are examples of possible substituents:

Halogen, in particular chlorine, hydroxyl, lower alkyl, preferably up to 5 carbon atoms, lower alkoxy, preferably up to 5 carbon atoms, sulfo or carboxyl. The compounds of the above general formulae not only prevent the fogging and the loss of sensitivity upon storage of the silver halide emulsions, but also produce a further increase in sensitivity.

A variety of suitable radicals is thus available by which the various properties of the compounds, for example, their solubility in water, can be influenced.

Suitable compounds are, for example:

me CH=N-CH(CH2)2-OO OK COOK (XI) OH tert.O4H CH=NC-H-(CH2)2OO OK COOK (XII) on Q CH=N(IJH(OHz)2-O OK COOK x111 in C4Hv0 l-CHz-NH-OHs-C O OH (XIV) ()H Br-QCHz-NH-CHr-O 0 OH HO 0 00011: 1-0156-0 0 0K (XVI) OH Cl CH=NCHzCHz-SO:N2.

l or

(XVII) Most of the above compounds have been described in the literature, e.g., by P. Pfeiifer, 1. pr. Chem. (2), 159, 313 (1941); Fraenkel-Conrat, J. Biol. Chem. 174, 827 (1948); Bergmann, Enslin, Zervas, Berichte, vol. 58, 1038 (1925). The azomethine compounds may 'be prepared by reacting, in aqueous solution, one mol of an alkali metal salt of an amino acid with one mol of an :aldehyde which may be substituted. The hydrogenation of the azomethine compounds is easily performed in aqueous solution with the aid of a Raney nickel catalyst.

Compounds XVI and XVII which contain a sulfo group are prepared in known manner by reacting the benzaldehyde with taurine or a derivative thereof.

The compounds of the present invention can be added to all photographic silver halide emulsions, the silver halide of which may consist of silver chloride, bromide, iodide or mixtures thereof, although silver iodo bromide emulsions are preferred.

As binding agent for the light-sensitive silver halide emulsion layer can be used hydrophilic colloidal materials, such as proteins, in particular gelatine, synthetic resins for instance, polyvinyl compounds, such as polyvinyl alcohol, polyvinyl pyrrolidone, or the like.

The emulsions can be further chemically sensitized by any of the known compounds and procedures, for example, the emulsions can be treated with labile sulfur compounds, such as sodium sulfite, thiourea, thiocyanates, alkali salts of thiocyanates, or salts of the noble metals, such as ruthenium, rhodium, palladium, iridium, and platinum. Representative compounds are ammonium chloropalladate, potassium chloroplatinate, and sodium chloropalladite. The emulsions can also be chemically sensitized with gold salts such as potassium chloroaurite, potassium aurithiocyanate potassium ohloroaurate, auric trichloride and 2-aurosulfobenzthiazole methochloride. The emulsions can also be optically sensitized with, for example, cyanine or merocyanines.

Most of the known photographic stabilizers are suitable as basic stabilizer in combination with the compounds according to the invention. In particular suitable are:

(1) Organic mercapto compounds as described, for example, in the United States Patents Nos. 2,728,663 665 (2) Quaternary benzthiazoles as described, for example, in United States Patents Nos. 2,131,038 and 2,694,716;

(3) Triazoles as disclosed in United States Patent No. 2,444,608;

(4) Azaindenes or azaindolizenes, more specially tetraazaindolizenes which are described in the publications of Birr: Z. wiss. Phot., vol. 47 (1952) pages 2 to 27; Phot. Korresp., vol. 99 (1963) page 163; Ber. d. chem. Ges., vol. 11, pages 1401-1403, and United States Patents Nos. 2,444,605/ 607, 2,450,397, 2,444,609, 2,713,- 541, 2,713,181, 2,716,062, 2,735,769, 2,756,147 or 2,772,164.

The basic stabilizers are added in an amount of 5 to 2000 mg. per liter of the emulsion.

As polyalkylene oxides there may be used the condensation products of alkylene oxides preferably ethylene oxide, with each other or with aliphatic alcohols, acids and amines or phenols. Polyethylene oxides which contain quaternary nitrogen groups are also suitable. It is preferred to use products which have a molecular weight of at least 1500 preferably of between 1500 and 3000.

The quantity to be used depends on the silver halide content of the emulsion and varies between 0.01 g. and 1 g. per 1 kg. of emulsion. The optimum quantity must be 'determined for each emulsion.

The ortho-h-ydroxybenzylor benzylideneamino compounds according to the invention are preferably added to the emulsion before chemical ripening or after-ripening. The solubility of the compounds of the invention is dependent upon the substituents, some are soluble in organic solvents, others in Water or aqueous solutions of acids or alkalis, such as alkali metal hydroxides, carbonates, phosphates or the like.

The compounds are used in concentration of 0.01 g. to 1 g. per 1 kg. emulsion (preferably 0.35 g./kg.). The optimum quantity to be added depends on the compound and on the type of emulsion. It may easily be determined by a. few tests. The compounds may also be incorporated in the finished photographic layer in a bath.

The stabilizers according to the invention can also be used for color photographic materials. The color couplers can be incorporated into the emulsion layer in a dissolved diffusion-resistant form. According to another method the color coupler is first dissolved in an oily organic material and this combination is then dispersed in a finely divided state throughout the emulsion. The developer according to the invention can also be used in those processes in which the so-called Successive Colorant Formation is applied. In this process the color coupler is incorporated into the colorforming developer composition. The successive color formation in each of the single layers of a multilayer material is obtained by controlled penetration of the processing solution. For example, in an integral tripack it is possible by means of a loaded dye coupling developer to develop the top layer of the material without affecting the lower emulsion layers if the time of development is carefully controlled.

Example 1 A very highly sensitive silver bromide iodide gelatine emulsion containing 4 mol. percent of iodide is prepared according to common practice. The emulsion contains silverhalide in an amount corresponding to 50 grams of silver per liter. The chemical ripening or after-ripening is performed in the usual manner. As ripening additives are used 35 to 40 mg. of KBr per liter of emulsion and a gold thiocyanate solution. This emulsion is divided into 3 parts, A, B and C.

Part A is used for comparison without further additives. Part B is treated with 300 mg./l. of compound 1. Part C is treated with 600 mg./l. of compound 1.

All three samples A, B and C are after-ripened until the maximum sensitivity is obtained. Thereafter, they are sensitized panchromatically adding one or more suitable sensitizing dyes. In this state of the production are further added a stabilizer in an amount of 200 mg. per liter, for example, an azaindolizine, particularly 7-hydroxy-5- methyl-triazaindolizin and 200 mg. per liter of a polyethylene oxide, having a molecular weight of about 2000. The final emulsion is applied to a conventional support, such as a film of cellulose acetate, polycarbonate on the basis of bis-hydroxy-phenyl alkanes, polyesters, in particular of terephthalic acid and ethylen glycol, and the like.

After five months storage, a portion of the photographic materials prepared in this way is stored for 3 days in a heating cupboard at 60 to compare it with the corresponding samples which have been stored at normal temperature. All the samples are then exposed and processed in the usual way.

The result is shown in Table 1:

With regard to the figures for sensitivity, it should be noted that an increase in sensitivity of 3 corresponds to an increase by one light stop.

Example 2 A very highly sensitive silver iodo bromide emulsion as described in Example 1 is divided into three parts, A, B, and C.

Part A is tested without further additives for comparison. Part B is treated with 300 mg./l. of compound IV. Part C is treated with 600 mg./l. of compound IV.

The three samples A, B and C are now treated as indicated in Example 1, the photographic material thus produced is stored for five months, a portion of the material is exposed for three days to a temperature of 60 in a heating cupboard and this material is then exposed and developed and compared with the corresponding samples which have been stored at normal temperature.

The results are shown in Table 2:

It will be seen from this table that the optimum quantity of additive of compound IV (Test B) must be determined in each case.

Example 3 A very highly sensitive silver iodo bromide emulsion described in Example 1 is divided into three parts, A, B and C.

Part A is ripened without further additives to be used for comparison.

Part B is treated with 300 mg./l. of compound VIII.

Part C is treated with 600 mg./l. of compound VIII.

All three samples A, B and C are then treated as indicated in Example 1, the photographic material thus produced is stored for five months and a portion of the material is subjected for three days to a temperature of 60 in a heating cupboard. The material is then exposed and developed as also, for comparison, the corresponding samples which have been stored at normal temperature.

The results are summarised in Table 3:

TABLE 3 Sensitivity Gamma Fogging Part A:

N onnal storage Typical O. 55 0. 20 Heating cupboard 1.5 O. 55 0. 43

Part B:

Normal storage Typical 0. 55 0. 20 Heating cupboard. =|=0 0. 5 0. 25

art 0:

Normal storage 0. 55 O. 26 Heating cupboard- :l: 0. 5 0. 33

The compounds of the present invention can be used in their acid form. The compounds can further be applied as salts of alkali metals, in particular sodium or potassium, or salts of ammonia or organic amides.

We claim:

1. A photographic silver halide emulsion, wherein the vehicle for the silver halide is a water-permeable hydro philic colloid and wherein said emulsion contains (1) an effective amount of a basic stabilizer;

(2) a sensitizing amount of a polyalkylene oxide and (3) an effective amount of a compound selected from those having the following formulae:

and

wherein X is a divalent radical of the group consisting of alkylene, having up to 5 carbon atoms and arylene and wherein R represents an acid radical of the group consisting of sulfo carboxylic -OSO H and a salt of the said acid radicals and both the 7 benzene ring and X can be substituted by halogen, hydroxyl, lower alkyl, lower alkoxy, sulfo or carboxyl.

2. A photographic silver halide emulsion as defined in claim 1, wherein the basic stabilizer is a member of the group consisting or organic mercapto compounds, quaternary benzthiazoles, triazoles, azaindenes and azaindolizines.

3. A photographic silver halide emulsion as defined in claim 1, wherein the basic stabilizer is an azaindolizine.

4. A photographic silver halides emulsion as defined in claim 1, wherein the polyalkylene oxide has a molecular Weight of at least 1500.

5. A photographic silver halide emulsion as defined in claim 4, wherein the polyalkylene oxide is a condensation product of alkylene oxide with a compound of the group consisting of aliphatic alcohols, aliphatic acids, aliphatic amines and phenols.

8 6. A photographic silver halide emulsion as defined in claim 1, which are additionally sensitized with a labile sulfur compound and a gold salt.

7. A photographic silver halide emulsion as defined in 5 claim 1, which contains the following compound:

No references cited.

NORMAN G. TORCHIN, Primary Examiner. JOHN H. RAUBITSCHEK, Assistant Examiner. 

1. A PHOTOGRAPHIC SILVER HALIDE EMULSION, WHEREIN THE VEHICLE FOR THE SILVER HALIDE IS A WATER-PERMEABLE HYDRO PHILIC COLLOID AND WHEREIN SAID EMULSION CONTAINS (1) AN EFFECTIVE AMOUNT OF A BASIC STABILIZER; (2) A SENSITIZING AMOUNT OF A POLYALKYLENE OXIDE AND (3) AN EFFECTIVE AMOUNT OF A COMPOUND SELECTED FROM THOSE HAVING THE FOLLOWING FORMULAE: 